This invention relates to current measuring techniques, and more particularly relates to current measuring techniques employing a Hall generator.
Hall generators for measuring the current carried through a conductor have been known in the past. However, the accuracy of such devices has suffered in the past due to inadequate regulating, current biasing and readout circuits associated with the Hall generator. Although coiled metal strips having the configuration described herein have been used in the past in connection with Hall generators, the fabrication of the coils from silicon steel has limited their usefulness.
Accordingly, it is an object of the present invention to provide an improved constant current circuit for biasing a Hall generator by means of a sample voltage proportional to the current flowing through the Hall generator, a reference voltage, and means for comparing the reference and sample voltages.
Another object of the invention is to provide a bias circuit of the foregoing type in which the Hall generator and an adjustable portion of the circuit are held within a probe which can be placed around the conductor carrying the current to be measured, and in which the remaining portion of the bias circuit is contained in a separate cabinet connected to the probe through a cable, so that Hall generators with different characteristics can be adjusted to work interchangeably with like bias circuits.
Still another object of the present invention is to provide a readout for the Hall generator in which the Hall output voltage is conducted to the inputs of at least one operational amplifier which floats in relationship to the power supply operating the amplifier.
Yet another object of the present invention is to provide a readout circuit of the foregoing type in which a meter for indicating the current to be measured is connected in the feedback loop of an operational amplifier having inputs adapted to receive the Hall voltage.
Another object of the present invention is to provide a method of detecting defects in a vehicular alternator by measuring the fluctuating current produced by the alternator.
Still another object of the present invention is to provide a method of the foregoing type in which the fluctuating current is attenuated below a predetermined frequency.
Yet another object of the present invention is to provide a probe of the foregoing type in which the magnetic field produced by the current to be measured is concentrated in the area adjacent the Hall generator by means of a toroidal, laminated core comprising nickel and iron.
Another object of the invention is to provide an improved regulator in which the voltage drop is sufficiently low to enable operation from a partially discharged vehicular battery.